Use Case Diagrams

In addition to introducing use cases as primary elements in software development, Jacobson (1994) also introduced a diagram for visualizing use cases. The use case diagram is also now part of the UML.

Many people find this kind of diagram useful. However, I must stress that you don't need to draw a diagram to use use cases. One of the most effective projects I know that used use cases involved keeping each one on an index card and sorting the cards into piles to show what needed building in each iteration.

Figure 3-2 shows some of the use cases for a financial trading system.

Figure 3-2. Use Case Diagram

Actors

An actor

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